Similarities
They are produced in many media
Both include sculptures, illuminated manuscripts, stained glass, metal works and mosaics.
Differences
They belong to different periods.
In the early part of the period, works in the so-called "minor arts" or decorative arts, such as metalwork, ivory carving, enamel and embroidery using precious metals, were probably more highly valued than paintings or monumental sculpture of the renainsance art.

In Medieval times there were less artist. In Renaissance time, more artist came around like Boticelli, Leonardo da Vinci, and the Medici family. That's why Renaissance means "rebirth". It's like a rebirth of the art culture.